Transparent conductor pattern structure of a capacitive touch panel comprising a plurality of conductor cells

ABSTRACT

Disclosed is a conductor pattern structure of a capacitive touch panel. First-axis conductor assemblies and second-axis conductor assemblies are formed on a surface of a substrate. Each first-axis conductor assembly includes a plurality of first-axis conductor cells that are interconnected by first-axis conduction lines. An insulation layer is formed on a surface of each first-axis conduction line. Each second-axis conductor assembly includes a plurality of second-axis conductor cells that are interconnected by second-axis conduction lines. Each second-axis conduction line extends across the insulation layer of the associated first-axis conduction line.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation Application of Ser. No. 13/401,854,filed Feb. 22, 2012, now U.S. Pat. No. 8,610,687, which is acontinuation of Application No. 11/842,747, filed Aug. 21, 2007, nowU.S. Pat. No. 8,217,902, by the present inventors, which is incorporatedherein by reference.

FIELD OF THE INVETION

The present invention relates to the field of touch panel devices, andin particular to a conductor pattern structure of a capacitive touchpanel.

BACKGROUND OF THE INVETION

Touch panels have been of wide applications in the fields of householdappliances, communications, and electronic information appliances. Anexample of the common applications of the touch panel is an inputinterface of a personal digital assistant (PDA), an electricalappliance, or a game machine, etc. The current trend of integration of atouch panel and a display panel allows a user to use his or her fingeror a stylus to point a control icon shown on the panel in order toexecute a desired function on a PDA, an electrical appliance or a gamemachine, etc. The touch panel is also applied in a public informationinquiry system to provide an efficient operation system for the public.

A conventional touch panel comprises a substrate having a surface onwhich sensing zones are distributed for sensing a signal associated withthe touch of a user's finger or stylus to effect input and control. Thesensing zones are made of transparent conductive membranes, such asIndium Tin Oxide (ITO), whereby a user may touch the transparentconducive membrane corresponding to a specific location shown on thedisplay to effect operation of the device.

The most commonly known types of touch panels include resistive panel,capacitive panel, infrared sensing panel, electromagnetic sensing panel,and sonic sensing panel. The capacitive touch panel employs a change incapacitance caused between a transparent electrode and theelectrostatics of human body to induce a current based on which thetouch location can be identified. The capacitive touch panel isadvantageous in light transparency, hardness, precision, response time,touches cycles, operation temperature, and initiation force and is thusmost commonly used currently.

In order to detect the location where a finger or a stylus touches thetouch panel, a variety of capacitive touch panel techniques aredeveloped. An example is U.S. Pat. No. 6,970,160, which discloses alattice touch-sensing system for detecting a position of a touch on atouch-sensitive surface. The lattice touch-sensing system may includetwo capacitive sensing layers, separated by an insulating material,where each layer consists of substantially parallel conducting elements,and the conducting elements of the two sensing layers are substantiallyorthogonal to each other. Each element may comprise a series of diamondshaped patches that are connected together with narrow conductiverectangular strips. Each conducting element of a given sensing layer iselectrically connected at one or both ends to a lead line of acorresponding set of lead lines. A control circuit may also be includedto provide an excitation signal to both sets of conducting elementsthrough the corresponding sets of lead lines, to receive sensing signalsgenerated by sensor elements when a touch on the surface occurs, and todetermine a position of the touch based on the position of the affectedbars in each layer.

U.S. Pat. No. 4,233,522 discloses a capacitive touch panel comprising anarray of touch sensitive switch cells. Each switch cell includes a firstand a second pair of series connected capacitors energized by a commonsignal source, the array of switch cells being arranged so that thefirst pair of capacitors are connected in first groups of switch cells,such as rows, to a corresponding first plurality of signal detectors,and the second pair of capacitors are connected in second groups ofswitch cells, such as columns, to a corresponding second plurality ofsignal detectors, the junctions of each pair of capacitors of a singleswitch cell being selectively coupled to ground by the body or othertouch capacitive means for actuating a selected switch cell.

U.S. Pat. No. 4,733,222 discloses a capacitance variation sensitivetouch sensing array system including an array of electrodes, an array ofdrive lines, a drive signal generator, and an array of sense lines. Eachelectrode is a connected series of conductive tabs and forms either arow or a column of the electrode array. Each drive line is capacitivelycoupled to a plurality of the electrodes. The drive signal generatorgenerates and applies alternating signal packets to the drive lines. Thesense line is capacitively coupled to a plurality of the electrodes sothat signals are derived from the electrodes when drive signals areapplied to the drive lines. The number of electrodes is equal to theproduct of the number of drive lines and the number of sense lines.Based on values derived from signals on the sense lines, amicroprocessor provides information associated with touch by anoperator.

U.S. Pat. No 5,880,411 discloses a method for recognizing a positionmade by a conductive object on a touch-sensor pad. Signals are sent to acontrol circuit of a host to identify the touch position. U.S. Pat. Nos.6,414,671 and 5,374,787 disclose the same technique.

U.S. Pat. No. 7,030,860 discloses a transparent, capacitive sensingsystem particularly well suited for input to electronic devices. Thecapacitive sensor can further be used as an input device for a graphicaluser interface, especially if overlaid on top of a display device likean LCD screen to sense finger position and contact area over thedisplay.

U.S. Pat. No. 5,459,463 discloses a device for locating an objectsituated close to a detection area and a transparent keyboardincorporating the device. The device comprises a first set of detectionzones connected so as to thin lines which extend parallel to each otherand to a detection area, a second set of detection zones connected toeach other so as to form columns which extend perpendicularly to thelines, a scanning device which applies an electric signal to the linesand columns, and means for determining the position of an object bymeans of the scanning device.

U.S. Pat. No. 6,498,590 discloses a multi-user touch system including asurface on which antennas are formed. A transmitter transmits uniquelyidentifiable signals to each antenna. Receivers are capacitively coupledto different users, and the receivers are configured to receive theuniquely identifiable signals. A processor then associates a specificantenna with a particular user when multiple users simultaneously touchany of the antennas.

U.S. Pat. No. 5,847,690 discloses a unitary display and sensing device,which integrates liquid crystal display module elements of a liquidcrystal display module for detecting input on a flat panel displayscreen.

All the prior art references described above provide teaching ofdetection touch of a user on a touch panel and all are comprised ofstructures of touch sensing elements. However, these known devices areall of a construction including two capacitive sensing layers spacedfrom each other with an insulation material to effect capacitive effectbetween the layers. This makes the structure of the panel very thick andis thus against the trend of miniaturization. Further, the conventionalcapacitive touch panel comprises a substrate on both surfaces of whichtwo capacitive sensing layers are formed respectively. In this respect,through holes must be formed on the substrate to serve as vias andcircuit layering must be adopted to properly connect conductor elementsof the sensing layers. This complicates the manufacturing of thecapacitive touch panel.

Thus, it is desired to have a capacitive touch panel that overcomes theabove drawbacks of the conventional capacitive touch panels.

SUMMARY OF THE INVENTION

Thus, an objective of the present invention is to provide a capacitivetouch panel comprising a thin conductor pattern structure, whichconsists of a plurality of first-axis conductor assemblies and aplurality of second-axis conductor assemblies, each conductor assemblybeing comprised of a plurality of conductor cells interconnected byconduction lines, wherein the conduction lines extending in differentaxes are isolated from each other by an insulation layer.

Another objective of the present invention is to provide a capacitivetouch panel comprising a conductor pattern structure consisting offirst-axis conductor assemblies and second-axis conductor assemblies,both comprising conductors cells connected by conduction lines, theconductor cells and the conduction lines being formed on the samesurface of a substrate by known processes for manufacturing generaltransparent conductor layer, whereby when a user touches the surface ofthe touch panel, the first-axis conductor assemblies and the second-axisconductor assemblies that are touched by the user induce capacitiveeffect between adjacent conductor cells thereof.

According to the present invention, a solution to overcome the abovediscussed drawbacks of the conventional capacitive touch panels residesin that a conductor pattern structure is formed on a surface of asubstrate, comprising a plurality of first-axis conductor assemblies anda plurality of second-axis conductor assemblies that are extended indirections that are substantially perpendicular to each other and thatcomprise a plurality of equally-spaced first-axis conductor cells andequally-spaced second-axis conductor cells respectively, and first-axisconduction lines and second-axis conduction lines interconnecting thefirst-axis conductors along the first axis and the second-axisconductors along the second axis respectively, wherein an insulationlayer is provided to cover a surface of each first-axis conduction lineto isolate the first-axis conduction line from the associatedsecond-axis conduction line.

According to the present invention, a plurality of first-axis conductorassemblies and a plurality of second-axis conductor assemblies, whichconstitute the conductor pattern structure of a capacitive touch panel,are formed on the same surface of a substrate, thereby simplifying thestructure and reducing the thickness of the structure. When theconductor cells of the first-axis conductor assemblies and the conductorcells of the second-axis conductor assemblies that are adjacent to eachother are touched by a user's finger, a capacitance variation signal isinduced, in response to the area of the adjacent conductor cells onwhich the finger of the user is laid, and then applied to a controlcircuit to identify the position where the user's finger touches thepanel. The first-axis conductor assemblies and the second-axis conductorassemblies of the conductor pattern structure can be formed on only onesurface of the substrate by the general circuit laying techniques. Thus,the present invention can be practiced in a simple process with highpassing rate and low costs.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be apparent to those skilled in the art byreading the following description of preferred embodiments thereof, withreference to the attached drawings, in which:

FIG. 1 is a plan view of a conductor pattern structure of a capacitivetouch panel in accordance with a first embodiment of the presentinvention;

FIG. 2 is a perspective view of a portion of the conductor patternstructure of the capacitive touch panel of the present invention.

FIG. 3 is a cross-sectional dew taken along line 3-3 of FIG. 2;

FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 2;

FIG. 5 illustrates the user's finger engaging a different point on thecapacitive touch panel in accordance with the present invention;

FIG. 6 illustrates a user's finger engaging a different point on thecapacitive touch panel of the present invention;

FIG. 7 illustrates a schematic view of a surface of a substrate on whicha plurality of first-axis conductor cells, first-axis conduction lines,signal transmission lines, and second-axis conductor cells are formed;

FIG. 8 illustrates a schematic view of the substrate surface on which aninsulation layer is formed to cover the surface of each first-axisconduction line, after the step of FIG. 7;

FIG. 9 illustrates a schematic view of the substrate surface on which asecond-axis conduction line is formed to connect between each pair ofadjacent second-axis conductor cells of the same second-axis conductorassembly, after the step of FIG. 8; and

FIG. 10 is a plan view of a conductor pattern structure of a capacitivetouch panel in accordance with a second embodiment of the presentinvention.

DETAILED DESCRIPTION

With reference to the drawings and in particular to FIGS. 1 and 2, ofwhich FIG. 1 illustrates a plan view of a conductor pattern structure ofa capacitive touch panel in accordance with a first embodiment of thepresent invention and FIG. 2 illustrates a perspective view of a portionof the conductor pattern structure of the capacitive touch panel,generally designated with reference numeral 12, is formed on a surface11 of a substrate 1. The conductor pattern structure 12 comprises aplurality of conductor assemblies 13 extending along a first axis, whichwill be referred to as “first-axis conductor assemblies”, and aplurality of conductor assemblies 14 extending along a second axis,which will be referred to as “second-axis conductor assemblies”. Each ofthe first-axis conductor assemblies 13 is parallel to other first-axisconductor assemblies 13, and each of the second-axis conductorassemblies 14 is parallel to other second-axis conductor assemblies 14.The first-axis conductor assemblies 13 are substantially perpendicularto the second-axis conductor assemblies 14. However, it is apparent thatthe first-axis conductor assemblies 13 and the second-axis conductorassemblies 14 can be arranged on the surface 11 of the substrate 1 at anincluded angle therebetween that is other than a right angle.

Each first-axis conductor assembly 13 is composed of a plurality offirst-axis conductor cells 131 that are lined up along the first axis,which is designated at “X” in the drawings, on the surface 11 of thesubstrate 1 in a substantially equally-spaced manner and a dispositionzone 15 is delimited between adjacent first-axis conductor assemblies 13and adjacent first-axis conductor cells 131.

A first-axis conduction line 132 connects between adjacent first-axisconductor cells 131 positioned along the first axis X so that thefirst-axis conductor cells 131 along the first axis X are electricallyconnected together to form a first-axis conductor assembly 13. In otherwords, the first-axis conductor cells 131 of the same first-axisconductor assembly 13 are connected together in cascade by thefirst-axis conduction lines 132. Each first-axis conductor assembly 13is further connected to a signal transmission line 16 a for transmittinga signal to a control circuit laid on a circuit board (both not shown).

Each of the conduction lines 132 has a surface 133 that is covered by aninsulation covering layer 17, which is made of a material featuringelectric insulation, and preferably a transparent insulation material,such as silicon dioxide. Each second-axis conductor assembly 14 iscomposed of a plurality of second-axis conductor cells 141 that arelined up along the second axis, which is designated at “Y” in thedrawings, in a substantially equally-spaced manner on the surface 11 ofthe substrate 1. Each second-axis conductor cell 141 is set in therespective second-axis conductor cell disposition zone 15.

A second-axis conduction line 142 connects between adjacent second-axisconductor cells 141 positioned along the second axis Y and extends overand across a surface of each insulation layer 17 so that the second-axisconductor cells 141 of the same second-axis conductor assembly 14 areconnected together. In other words, the second-axis conductor cells 141of the same second-axis conductor assembly 14 are connected together incascade by the second-axis conduction lines 142. Each second-axisconductor assembly 14 is further connected to a signal transmission line16 b for transmitting a signal to the control circuit.

Also referring to FIG. 3″ which shows a cross-sectional view taken alongline 3-3 of FIG. 2, and FIG. 4, which shows a cross-sectional view takenalong line 4-4 of FIG. 2, the first-axis conductor cells 131, thefirst-axis conduction lines 132, the second-axis conductor cells 141,and the second conduction lines 142 are made of transparent conductivematerial. The insulation layer 17 is interposed between the respectivefirst-axis conduction line 132 and the second-axis conduction line 142so that the second-axis conduction line 142 that connects adjacentsecond-axis conductor cells 141 of the second-axis conductor assembly 14extends across the respectively first-axis conduction line 132 in amutually-insulated manner.

The substrate 1 can be a glass substrate, and the first-axis conductorassemblies 13 and the second-axis conductor assemblies 14, and thefirst-axis and second-axis conduction lines 132, 142 are made oftransparent conductive film, such as ITO conductive film. In theembodiment illustrated, the first-axis conductor cells 131 and thesecond-axis conductor cells 141 are of a shape of substantially hexagongeometry contour. It is apparent that the conductor cells 131, 141 canbe of shapes of other geometry contours to effect an optimumdistribution of effective conductor surface.

FIG. 5 demonstrates a user's finger physically engaging a point on thecapacitive touch panel in accordance with the present invention, andFIG. 6 demonstrates the user's finger engaging a different point on thecapacitive touch panel of the present invention. When a user put his orher finger to touch a contact area (point), designated at “A,”, on thecapacitive touch panel of the present invention, the first-axisconductor cell 131 of the first-axis conductor assembly 13 and thesecond-axis conductor cell 141 of the second-axis conductor assembly 14,which are covered by the contact area A, induce a capacitor effecttherebetween and a signal caused thereby is transmitted through thesignal transmission lines 16 a, 16 b to the control circuit. The controlcircuit may then carry out computation to determine on which point onthe surface 11 of the substrate 1 the contact area A is set.

When the user moves his or her finger to another contact area B, thefirst-axis conductor cell 131 of the first-axis conductor assembly 13and the second-axis conductor cell 141 of the second-axis conductorassembly 14, which are covered by the contact area B, induce a capacitoreffect therebetween and a change occurs, which induces a signal that istransmitted through the signal transmission lines 16 a, 16 b to thecontrol circuit. The control circuit may then carry out computation todetermine on which point on the surface 11 of the substrate 1 thecontact area B is set.

FIGS. 7 and 8 are schematic plan views demonstrating manufacturing stepsof the conductor pattern of the capacitive touch panel in accordancewith the present invention, wherein FIG. 7 illustrates the schematicview of a surface of a substrate on which a plurality of first-axisconductor cells 131, first-axis conduction lines 132, signaltransmission lines 16 a, 16 b, and second-axis conductor cells 141 arejust formed, and FIG. 8 illustrates the schematic view of the substratesurface on which an insulation covering layer 17 is formed to cover thesurface of each first-axis conduction line 132, after the step of FIG.7. Further, FIG. 9 illustrates a schematic view of the substrate surfaceon which a second-axis conduction line 142 is formed to connect betweeneach pair of adjacent second-axis conductor cells 141 of the samesecond-axis conductor assembly, after the step of FIG. 8, to therebycomplete the manufacturing of the conductor pattern structure of thetouch panel in accordance with the present invention.

The manufacturing of the conductor pattern structure 12 can be carriedout with any known techniques, such as etching, sputtering, and screenprinting. Etching is taken as an example for manufacture of theconductor pattern structure as follows. First of all, a conductor film,of which an ITO transparent conductive film is an example, is formed onthe surface 11 of a cleaned substrate 1. Thereafter, screen printing isemployed to carry out etching mask printing process.

After the etching mask printing process, etching is carried out on thesurface 11, followed by film stripping. Thus, the first-axis conductorcells 131 of the first-axis conductor assemblies 13, the firstconduction lines 132, and the second-axis conductor cells 141 of thesecond-axis conductor assemblies 14, all being transparent andelectrically conductive, are formed on the substrate surface 11, asshown in FIG. 7. At this point, all the first-axis conductor cells 131of the same first-axis conductor assemblies 13 are electricallyconnected together and the first-axis conductor assemblies 13 arefurther connected to a plurality of signal transmission lines 16 a.

Thereafter, an insulation covering layer 17 is applied to cover thesurface 133 of each first-axis conduction line 132, as shown in FIG. 8.Then, a mask is formed with the printing technique to define thepositions of the second-axis conduction lines 142, followed byapplication of a transparent conductive layer to form the second-axisconduction lines 142 whereby the adjacent second-axis conductor cells141 along the second axis Y are each connected by the second-axisconduction lines 142 with each second-axis conduction line 142 extendingover and across the surface of the respective insulation layer 17, asshown in FIG. 9. Once the step is done, all second-axis conductor cells141 of the same second-axis conductor assemblies 14 are electricallyconnected together and the second-axis conductor assemblies 14 areconnected to the signal transmission lines 16 b.

When the etching technique described above is taken to form theconductor cells and the conduction lines on the substrate surface,different pattern can be formed with etching areas. defined by differentetching masks to similarly form a conductor pattern structure. Forexample, in the first etching step, only the first-axis conductor cells131 and the first-axis conduction lines 132 of the first-axis conductorassemblies 13 are formed on the substrate surface 11, but not thesecond-axis conductor cells 141 of the second-axis conductor assemblies14. Thereafter, the same etching technique is taken again to form thesecond-axis conductor cells 141 and the second-axis conduction lines 142on the substrate surface 11, with the second conduction lines 142extending over and across the surfaces of the associated insulationlayers 17.

In the embodiment discussed previously, the first-axis conductor cellsand the second-axis conductor cells are each formed on the substrate inan array form to constitute the conductor pattern structure of thecapacitive touch panel. Based on the same philosophy, a small number ofconductor cells can also be used to construct a conductor patternstructure of the capacitive touch panel. This is illustrated in FIG. 10as a second embodiment of the disclosure, wherein two adjacentfirst-axis conductor cells 31, 32 are formed on a surface 21 of asubstrate 2 and a signal transmission line 34 is connected to theconductor cell 32. A first-axis conduction line 33 connects between theadjacent first-axis conductor cells 31, 32. An insulation layer 4 isformed on a surface of the first-axis conduction line 33.

Along an axis that is different from the first-axis conductor cells 31,32, two adjacent second-axis conductor cells 51, 52 are arranged and asecond-axis conduction lines 53 connects between the adjacentsecond-axis conductor cells 51, 52 by extending over and across asurface of the insulation layer 4. The conductor cell 52 is alsoconnected to a signal transmission line 54.

Although the present invention has been described with reference to thepreferred embodiments thereof, it is apparent to those skilled in theart that a variety of modifications and changes may be made withoutdeparting from the scope of the present invention which is intended tobe defined by the appended claims.

What is claimed is:
 1. A transparent conductor pattern structure of acapacitive touch panel, the transparent conductor pattern structurecomprising: a plurality of conductor cells disposed on a surface of asubstrate having electrically connected rows of conductor cells andelectrically connected columns of conductor cells; and a plurality ofdiscrete insulation layers arranged to electrically insulate theelectrically connected rows of conductor cells from the electricallyconnected columns of conductor cells, wherein the plurality of conductorcells are shaped and arranged in an array on the substrate for detectionof a position of touch where a mutual capacitance changes between atleast one conductor cell of an electrically connected row of theelectrically connected rows of conductor cells and at least oneconductor cell of an electrically connected column of the electricallyconnected columns of conductor cells, and the plurality of conductorcells and the plurality of discrete insulation layers are transparent.2. The transparent conductor pattern structure as claim 1, furthercomprising a plurality of signal transmission lines formed on thesubstrate, wherein each signal transmission line connects to one of theelectrically connected rows of conductor cells or one of theelectrically connected columns of conductor cells.
 3. The transparentconductor pattern structure as claim 1, further comprising a pluralityof first conduction lines, wherein the electrically connected rows ofconductor cells are arranged on the surface of the substrate along afirst direction in a substantially equally-spaced manner, and each ofthe first conduction lines is disposed for forming an electricalconnection between adjacent conductor cells of the electricallyconnected rows of conductor cells.
 4. The transparent conductor patternstructure as claim 3, wherein the plurality of first conduction linescomprises a transparent conductive material.
 5. The transparentconductor pattern structure as claim 1, further comprising a pluralityof second conduction lines, wherein the electrically connected columnsof conductor cells are arranged on the surface of the substrate along asecond direction in a substantially equally-spaced manner, and each ofthe second conduction lines is disposed for forming an electricalconnection between adjacent conductor cells of the electricallyconnected columns of conductor cells.
 6. The transparent conductorpattern structure as claim 5, wherein the plurality of second conductionlines comprises a transparent conductive material.
 7. The transparentconductor pattern structure as claim 1, wherein the plurality ofconductor cells have a contour of hexagonal shape.
 8. The transparentconductor pattern structure as claim 1, wherein a substantial portion ofthe conductor cells of the electrically connected rows of conductorcells are exposed to the plurality of discrete insulation layers.
 9. Acapacitive touch panel having a transparent conductor pattern structure,the capacitive touch panel comprising: a plurality of conductor cellsdisposed on a surface of a substrate having electrically connected rowsof conductor cells and electrically connected columns of conductorcells; a plurality of discrete insulation layers arranged toelectrically insulate the electrically connected rows of conductor cellsfrom the electrically connected columns of conductor cells; and acontrol circuit electrically connected to the electrically connectedrows of conductor cells and the electrically connected columns ofconductor cells, wherein the plurality of conductor cells are shaped andarranged in an array on the substrate for detection of a position oftouch where a mutual capacitance changes between at least one conductorcell of an electrically connected row of the electrically connected rowsof conductor cells and at least one conductor cell of an electricallyconnected column of the electrically connected columns of conductorcells, and the plurality of conductor cells and the plurality ofdiscrete insulation layers are transparent.
 10. The capacitive touchpanel as claim 9, further comprising a plurality of signal transmissionlines formed on the substrate, wherein each signal transmission lineconnects between one of the electrically connected rows of conductorcells and the control circuit or between one of the electricallyconnected columns of conductor cells and the control circuit.
 11. Thecapacitive touch panel as claim 9, further comprising a plurality offirst conduction lines, wherein the electrically connected rows ofconductor cells are arranged on the surface of the substrate along afirst direction in a substantially equally-spaced manner, and each ofthe first conduction lines is disposed for forming an electricalconnection between adjacent conductor cells of the electricallyconnected rows of conductor cells.
 12. The capacitive touch panel asclaim 11, wherein the plurality of first conduction lines comprises atransparent conductive material.
 13. The capacitive touch panel as claim9, further comprising a plurality of second conduction lines, whereinthe electrically connected columns of conductor cells are arranged onthe surface of the substrate along a second direction in a substantiallyequally-spaced manner, and each of the second conduction lines isdisposed for forming an electrical connection between adjacent conductorcells of the electrically connected columns of conductor cells.
 14. Thecapacitive touch panel as claim 13, wherein the plurality of secondconduction lines comprises a transparent conductive material.
 15. Thecapacitive touch panel as claim 9, wherein the plurality of conductorcells have a contour of hexagonal shape.
 16. The capacitive touch panelas claim 9, wherein a substantial portion of the conductor cells of theelectrically connected rows of conductor cells are exposed to theplurality of discrete insulation layers.